Field of the Invention
The present invention relates to a hair dryer, and more particularly to a hair dryer capable of automatically controlling a driving voltage and an output.
Description of the Related Art
A hair dryer is a household appliance in which a fan is attached to a shaft of a small motor, to blow out a stream of hot air generated by a heater through an air outlet. Such a hair dryer is also referred to as a “blower”. Such a hair dryer may be used to remove moisture from hair or style hair, using a stream of hot air.
Meanwhile, in such a hair dryer, the heater mounted therein is designed to operate at a commercial voltage. Accordingly, when the heater operates at a commercial voltage of 110V, resistance of a heating coil thereof should be set to meet 110V supply power. On the other hand, when the heater operates at a commercial voltage of 220V, resistance of a heating coil thereof should be set to meet 220V supply power.
If the 110V hair dryer is connected to a 220V commercial power source, there is a possibility that a fire is generated and, as such, the user is exposed to great danger.
In the case of a 1,500W 110V hair dryer, a heater having a resistance of about 8Ω is used to generate a desired output. When the 100V hair dryer is connected to a 220V commercial power source, an output of 6,000W is momentarily generated and, as such, the heater of the hair dryer is overheated, thereby resulting in generation of a fire. In this case, the hair dryer is damaged and, as such, can no be longer used.
Meanwhile, most hair dryers employ a DC motor operating at a DC voltage of about 28 to 38V in accordance with characteristics of the hair dryers. Since the input voltage of such a hair dryer is an AC voltage, it is necessary to convert the AC voltage into a DC voltage. To this end, a heating wire is arranged at an input terminal of the motor, to drop the commercial voltage, and the dropped voltage is bridge-rectified, to drive the DC motor. For this reason, there is a problem in that it is impossible to arrange both a heating wire for 110V and a heating wire for 220V in order to use the heating wires as motor loads for voltage drop.
On the other hand, when a 220V hair dryer is used at a 110V commercial voltage, the amount of air stream is considerably reduced due to a relatively low motor voltage. In this case, accordingly, the hair dryer cannot perform a desired intrinsic function thereof.
In order to solve the above-described problems, a hair dryer operating on electric power of either 110V or 220V has been proposed. In this case, a manual switch is included in the hair dryer, to enable the user to directly operate the switch.
In this hair dryer, however, there is a problem in that the user is directly exposed to danger, as mentioned above, when the user carelessly connects the hair dryer to a 220V commercial power source under the condition that the hair dryer has been switched for 110V.